1. Field of the Invention
The present invention relates to the technical field of key scanning and, more particularly, to an ultra-low power wakeup circuit device.
2. Description of Related Art
With the advanced technologies, the electronic skills have been developed from the earliest vacuum tubes and transistors to the integrated circuit (IC) chips, which have been widely used. Thus, a variety of electronic products have gradually become indispensable necessities in daily living for modern people. Many articles have been increasingly electrized for the purpose of convenient use.
Many control methods used in electronic products, such as computers, mobile phones, and the like, typically use a button control. Generally speaking, the methods of detecting the scanning of keyboard buttons are grouped into two types, i.e., a matrix-type scan and a triangular-type scan.
FIG. 1 is a schematic diagram illustrating a circuit of a typical triangular-type scan keyboard. As shown in FIG. 1, the circuit includes a triangular-type scan keyboard controller 100, six vertical scan lines VS11-VS16, six horizontal scan lines HS11-HS16, and six I/O pins IO0-IO5. When a keyboard button detection starts, the I/O pins IO0-IO5 of the horizontal scan lines HS11-HS16 sequentially output scan pulses. More particularly, when one of the I/O pins IO0-IO5 outputs the scan pulse, the remaining pins perform the detection. For example, when the I/O pin IO1 outputs the scan pulse, the I/O pins IO1-IO5 perform the detection. Further, if the I/O pin IO1 outputs the scan pulse and the button 101 is pressed, the vertical scan line VS15 and the horizontal scan line HS11 are short-circuited. Accordingly, the scan pulse is received by the I/O pin IO4. In this case, the triangular-type scan keyboard controller 100 can determine that the button 101 is pressed.
As compared with a matrix-type scan keyboard, both have the keyboard controller with six I/O pins, but the triangular-type scan keyboard controller 10 can control 15 buttons while the matrix-type scan keyboard controller can control 9 buttons. In other words, under the consideration of the I/O resources of an integrated circuit (IC), the triangular-type scan keyboard controller can reduce the number of used I/O pins in view of the same number of buttons to be controlled.
However, the triangular-type scan keyboard controller chip typically consumes the current ranging from several hundreds of μA to several mA, which is still acceptable with respect to a high-power system but unacceptable by, for example, the sleep current of a remote controller that is limited to several μA.
To reduce the current consumption, US Patent Publication No. 2010/0259424 has disclosed a power saving method in a sleep mode. The method provides a first clock source and a second clock source, wherein a frequency of the second clock source is much lower than a frequency of the first clock source. In a normal mode, a scan pulse from the I/O pins is sequentially outputted according to the frequency of the first clock source. In the sleep mode, the scan pulse from the I/O pins is sequentially outputted according to the frequency of the second clock. Namely, in the sleep mode, the second clock source with relatively lower frequency is used to reduce the current consumption.
However, for either the matrix-type or the triangular-type scan keyboard, the keys may be blocked due to the humidity or other factors. For example, a user, who sits on a sofa and uses a remote control to select and watch one program, may sit on the remote control in carelessness, so that the keyboard controller chip cannot enter in the sleep mode and thus wastes the power.
Therefore, it is desirable to provide an improved ultra-low power wakeup circuit device to mitigate and/or obviate the aforementioned problems.